Shelf Sea Biogeochemistry blog

Friday, 21 November 2014

21 November, 2014 09:05

Ocean research cruise blog of Jonathan Sharples

We arrived at the central Celtic Sea mooring site yesterday at 0930.
Recovering the moorings was delayed a couple of hours while we waited
for the wind to drop a little, but we began pulling them out of the sea
shortly after lunch.

We have a fairly complex array of instruments on the moorings out
here. There’s a weather buoy, provided to our project by the UK Met
Office, plus a Cefas Smartbuoy that samples the surface biology and
chemistry. The Met Office buoy doesn’t need servicing – they are
designed to stay at sea sending back weather information for about 2
years. The Cefas buoy is looked after by Cefas scientists also working
on this project. That leaves 3 other components that we need to service.
The first mooring is a vertical line of acoustic current meters,
anchored to the seabed and stretched upward by large buoys. These
current meters are being used to measure turbulence in the sea, which
allows us to calculate the supplies of nutrients towards the sea surface
and how carbon is being mixed downward.

curretn meter buoy recovery

The second mooring is a
relatively simple steel frame containing two acoustic current meters;
this frame sits on the seabed, with the current meters looking upward
and every 5 minutes measuring the flow of water in a series of 4 metre
thick layers throughout the entire depth. Finally, the most complex of
the moorings is a line holding about 25 temperature and salt loggers,
anchored to the seabed and stretched up towards the sea surface by
several buoys. These loggers, sampling every 1 minute, show us how
stratified the water is, where in the water the thermocline is, and also
if there are any waves running along the thermocline. All 3 moorings
came up OK, though the string of loggers popped up about 1 km away from
where we expected it to appear, requiring a bit of nifty ship
manoeuvring by the captain to grab the mooring before it drifted onto
the Cefas buoy. Once everything was on board, the National Marine
Facilities engineers, along with Jo Hopkins and Chris Balfour from the
Oceanography Centre in Liverpool, downloaded data, re-batteried
instruments, and got the new mooring wires wrapped onto the winches
ready for deployment.